The NBS-LRR Gene Family in Psidium guajava: Potential Applications of Genetic Markers for Germplasm Characterization and Disease Resistance

The NBS-LRR gene family plays a central role in plant immune responses; however, its characterization in Psidium guajava, a crop of global socioeconomic relevance, remains unexplored. In this study, 279 NBS-LRR genes were identified and classified into subclasses (CNL, TNL, RNL, and others) based on conserved domains. Comprehensive analyses were conducted to investigate gene structure, protein properties, subcellular localization, chromosomal distribution, conserved motifs, and domain organization. Phylogenetic analyses were conducted using full-length NBS-LRR protein sequences from P. guajava, Arabidopsis thaliana, and functionally validated nematode resistance genes revealed that several P. guajava proteins clustered with known nematode resistance genes. Notably, orthologs of Mi-1, Gpa2, and Gro1-4 were identified, suggesting their potential role in nematode resistance. Furthermore, microsatellite analysis detected 25 SSRs within NBS-LRR protein-coding sequences, including two NBS-LRR genes, orthologous to Mi-1, CaMi, Hero, and Gpa2 and Cre1 and Cre3, respectively, containing microsatellite motifs. Variant calling analysis revealed a broad distribution of SNPs across the Psidium guajava genome, with NBS-LRR genes showing a high frequency of missense and synonymous variants, suggesting regions potentially associated with adaptation and pathogen resistance. These findings provide novel insights into the genetic basis of disease resistance in P. guajava and its interactions with pathogens. This study represents a significant step toward understanding the molecular mechanisms of pathogen resistance in P. guajava, with implications for sustainable crop protection and productivity.